THE SUNHydrostatic equilibrium

The source of the sun’s energy is

NUCLEAR FUSION

H + H → He

In this process…

A small amount of (nuclear) mass is converted to energy.

Proton-proton chain

Specifically, gamma rays

High energy, short wavelength

When a gamma ray photon collides with an H or He nucleus

It is ABSORBED then

RE-EMITTED

As this happens over and over,

The photon eventually photon loses some of its energy and changes to a different form of E-M energy. (The nuclei of atoms can absorb energy (from a gamma ray or a neutron, for instance), which produces an unstable nucleus which can then go to a lower energy by emitting a gamma ray, or by splitting (fission) in the case of a few atoms.)

By the time it reaches the surface which may take 15 million years) it may have been converted to….

Visible light….

Longer wavelength, lower frequency

WHY SO LONG?

The sun’s great mass/gravity squeeze the gas below the surface so the particles are very close together.

According to Gay-Lussac’sLaw

TEMEPERATURE AND PRESSURE ARE

DIRECTLY RELATED SO….

Gay-Lussac’s Law

More squeezing, the gas gets hotter

The hotter the gas gets, the more it wants to spread out

If it can’t spread out

The pressure increases.

More pressure, more higher temperature--

The sun’s core has a high temperature—15 million Kelvins

The higher the temperature

The greater the gas pressure pushing OUT from the core.

It is this pressure

THAT BALANCES THE GRAVITY OF THE

SUN

THE BALANCE BETWEEN GAS PRESSURE AND GRAVITY IS CALLED

HYDROSTATIC EQUILIBRIUM